It's easy to picture the traditional workstation. Simply imagine a high-powered UNIX computer, somewhere between a PC and a minicomputer, that tackles power-hungry applications like computer-aided design/engineering (CAD/CAE), computer-aided manufacturing (CAM), graphics, or publishing. Yet today, even the least expensive PCs can outperform the workstations of just 10 or 15 years ago.
With embedded microprocessors showing up just about everywhere, the term "workstation" takes on a new meaning. For example, musicians may be familiar with Yamaha's Tyros2 Arranger Workstations. These powerful keyboards let performers compose music and "add tracks" without desktop PCs because the PC is built in.
In industrial automation systems, workstations often mean dedicated human-machine interfaces (HMIs) located in the control room, in the engineering department, or on the plant floor. But today's distributed industrial networks are migrating from proprietary to Ethernet TCP/IP.
They let HMIs/workstations collect industrial data from any number of industrial controllers, massage it, and present it to engineers and operators who often have to make split-second decisions. This distributed model can be applied to test and measurement equipment, whether it's located in a test stand or on the design engineer's bench, to provide enterprise-wide information and distributed engineering across the globe.
Some vendors call their scopes and calibrators workstations because they feature embedded PCs. Perhaps digital storage oscilloscopes (DSOs) with an embedded PC—one that lets designers run the software they use on their desktops (e.g., LabView, MS Excel, MS Word, and Microsoft's OneNote notetaking/collaboration program)—qualify as workstations. Maybe your idea of a "workstation" includes the furniture that houses your test equipment.
Regardless of the definition, a few things are clear. Most users clamor for simplicity, ease of use, accuracy, repeatability, and reliability. With PC-based instrumentation, engineers are discovering the benefits of connectivity. They share design data with other engineers and suppliers, as well as measurement data with quality and test groups. While the general-purpose interface bus (GPIB) has served the industry well over the last 20 to 30 years, newer solutions promise more versatile and less expensive connections.
DO WE NEED A DEFINITION? A few engineers might consider testbench furniture to be a workstation. Perhaps Tektronix's TM500 series of modular test equipment represents a fine example of a bygone workstation. Its modules could be mixed and matched to suit an engineer's needs. This mainframe, pluginbased equipment didn't have any smarts compared to today's microprocessor-based instruments. Yet its modular design was durable, versatile, and elegant in its simplicity.Does a PC with plug-ins or an extension rack constitute a workstation? Possibly. According to Mike Jaynes, manufacturing engineer at New Star Lasers, today's PC-based plug-ins may display different problems. While they're ideal for production testing where setups can be called with pass/fail limits, they don't have a dedicated instrument's ease of use when the need arises for a quick measurement. Also, not all plug-ins can withstand the measurement of extremely high-voltage signal levels. Jaynes suggests that engineers who tend to work with digital voltage levels may find these PC-cardbased workstations viable.
For Alon Harpaz, electrical engineer at Danaher Motion, the term " workstation" first brings to mind the familiar box-monitor-keyboard-mouse setup. But he acknowledges that the concept can be extended to anything that allows a very flexible control approach and extensive data-manipulation capabilities.
It makes little difference if data plotting and analysis is conducted in MS Excel (or any spreadsheet) or with dedicated packages such as LabView. He further notes that the engineer should be free to explore meaning and information within data sets using appropriate and/or convenient tools. Engineers also shouldn't be limited by the hardware used to acquire the data.
Does "workstation" apply to a PCbased scope? Harpaz suggests that a workstation would allow data-analysis tools to be added. Using " workstations" to describe scopes that use an embedded form of Windows where Windows' functionality isn't directly accessible wouldn't be accurate.
Agilent's Infiniium 8000 series oscilloscopes can use LabView as the user interface to the scope (Fig. 1). In addition, they can run other Windows programs-like Excel or MatLab and programming languages such as MS Visual Studio.
An interesting application for running MatLab on a scope is to use the software as a real-time filter. Dan Monopoli, marketing engineer at LeCroy, says that engineers may have a proprietary algorithm or filter that they need to run before observing the measurement signal.
It's possible to take the data from the scope channel, send it into MatLab, process it in real time, and display its output in real time. Monopoli also notes the obvious advantage—designers don't need a PC on their bench, so they have space for other instruments.
Another advantage to using PCbased scopes and logic analyzers is connectivity (Fig. 2). "Since most of these instruments also have network connectivity, they're easy to configure with the user's PC to take advantage of word processors, spreadsheets, and database applications," says Steve Coan, design engineer at Relcom Inc., a manufacturer of industrial local-area-network (LAN) components.
"The new LabView 8 offering from National Instruments touts distributed applications," Coan continues. "Thus, the definition of workstation is changing and may ultimately depend upon the user's application to define what it really is."
Distributed software applications can help engineers automatically document tests to suit regulatory agencies, eliminating manual data entry. Jaynes' company, New Star Lasers, is an FDA-qualified (CFR Parts 210, 211, and 820) medical device development and manufacturing group specializing in surgical and cardiovascular lasers.
Like many pharmaceutical and food manufacturers, his company must comply with FDA record-keeping requirements. It manually conducts final product test measurements and enters them into a test report.
Electronic record keeping (FDA 21 CFR Part 11), which has become more prevalent in the food and pharmaceutical industries, could replace paper records. But for the most part, test-instrumentation vendors seem unaware of FDA 21 CFR Part 11 and how to implement it.
Fortunately, for those who have access to LabView software on their "workstations," help is on the Web. Log on to to National Instruments' Web site (www.ni.com) and search for "Using LabVIEW to Create FDA 21 CFR 11 Compliant Applications." System integrators and other third parties also are ready to assist.
SOFTWARE ISSUESIt doesn't matter if it's a PC-based waveform generator, logic analyzer, signal generator, spectrum analyzer, or scope. Engineers don't like to wade through "menu hell," as Jaynes calls it, to get a quick measurement. While they're okay for configuring a test stand, deeply nested menus slow the measurement process.Ken Koehn, program manager of system components at Agilent, notes that his company holds most of its scopes' menu structure at no more than two levels deep. Unlike the earliest DSOs, Infiniium scopes maintain the look and feel of an analog scope. According to Monopoli, large touchscreens (8.4 and 10.4 in.) also help satisfy customers who demand easier-to-use scopes.
Another way to make digital instruments less complicated and less expensive is to let users buy the functionality they need—and no more. While Koehn says that Agilent's customers generally have been asking for more complexity in today's 8000 series, limiting installed software modules to fit their applications makes lots of sense.
For example, engineers who need to design and test GSM phones or LAN chips can download the appropriate personality modules and pay for them as needed. Engineers designing audio equipment don't care about jitter analysis and shouldn't have to pay for an unused feature.
STANDALONES VS. PROGRAMMING NI's Darcy Dement, senior product manager of modular instruments, notes that design and test engineers performing measurements on the benchtop require interactive measurements to quickly verify their design and diagnose incorrect circuit behavior. Therefore, they often use traditional, standalone instruments on the benchtop to obtain "always on" performance and a fast time to measurement without programming.Harpaz says that when programming is necessary, LabView Virtual Instruments (VIs) provide a way to collect data from various measurement devices, i.e., laser interferometers, capacitive probes, and other mechanical metrology devices. Danaher Motion's QA group uses LabView VIs to analyze and export machine metrology data, which measures variables such as the straightness, pitch, yaw, and accuracy of moving axes.
VIs have simplified instrumentation configuration. According to Fluke marketing manager Hilton Hammond, the U.S. Department of Defense continues to push a common VI platform so engineers can plug in digital multimeters (DMMs) from Agilent, Fluke, or any other vendor and have them work in the same system. Engineers simply don't want to spend time dealing with the intricacies of writing drivers and programming in C or Visual Studio.
While VI development can still represent a significant time investment, National Instruments shortcuts the process for benchtop applications. Its Express VIs minimize benchtop measurement configuration and programming while maintaining a fully customizable GUI and development environment. According to Dement, Signal Express is a fully interactive measurement environment for benchtopapplications (Fig. 3). It requires no programming, and it offers built-in instrument control, analysis, visualization, and data storage.
HARDWARE Knowing what instrumentation hardware to use can save money. Walter Shawlee, president of Sphere Research Corp., thinks many companies are throwing money into higherend instrumentation when it isn't required. There's no reason to use a 6-GHz scope on analog audio or video signals when a 100-MHz, dual-trace scope will suffice, he says.
Shawlee also says that some of the high-end digital DMMs don't hold their accuracy as well as his older Fluke or Tek TX1, which are no longer available. Another engineer complained that his new DMM just doesn't update its display fast enough.
Here's Agilent's rule of thumb for selecting a DSO: signal bandwidth (Hz) = 0.5/signal rise time (s), and scope bandwidth = 2 signal bandwidth (for 3% errors). So, measuring a 1.0-ns rise time at 3% error requires a scope bandwidth of 1 GHz. For a fourchannel scope, multiply the scope bandwidth by 4 to get 4 Gsamples/s. On DMM update rates, says Koehn, today's DMMs manage 50,000 readings/s and can sample ac signals at 1.5 Msamples/s.
But wide bandwidths and fast sampling rates aren't the only important factors. Viren Javadekar, engineering manager of the Power Quality Correction Group at Schneider Electric, needs noise-free signals, isolation, and portability in a scope. He uses his Tektronix TPS2000 series scope to look for glitches and anomalies on threephase power systems.
A false glitch caused by noise can waste several days trying to solve a nonexistent problem. Because the scope has completely floating channels, there's no need for separate isolation devices between each phase and the scope's inputs. Javadekar employs the instrument on the bench in design and development, uses it on the plant floor for manufacturing testing, and carries it to sites for startup and troubleshooting.
PCs AND CARD CAGES Shawlee and other engineers have noted that some PCbased instruments (those that plug directly into a PC's PCI slot) are limited in usefulness. While they're inexpensive, they often emit or are susceptible to noise. Also, ground loop problems are common. According to NI director of measurement technology Ken Reindel, if these cards are designed properly in the first place, these issues become non-issues—whether the card lives in a PC or in a box."The problems that need to be solved to put precision, low-noise instrumentation in a PC environment are similar to those of building a traditional box product, because today's box products contain at least one microcomputer, display, power supply, and user interface much like a computer does," says Reindel. "Either way, the sensitive circuitry must be properly shielded, power supplies must be properly bypassed, and layout must be optimized to avoid interference-induced errors."
VXI (a VME-based card system) instruments represent a high-end solution to these PC issues, but they tend to be quite expensive. These industrial-strength, high-speed instruments-on-a-card work well in teststand applications for aerospace, military, automotive, and telecom applications but would be too expensive to be considered a workstation for the average design engineer.
UPGRADING FROM GPIB GPIB, the venerable communications link between test equipment and host computers, hasn't necessarily lost its effectiveness. However, as many industrial automation users are discovering, equipment based on readily available off-the-shelf (OTS) PC communication technology can be less expensive—and it may be even easier to install and configure.Harpaz notes that a significant portion of his company's test-instrumentation development effort was directed toward the actual means of communication with various metrology equipment, including an old laser interferometer that uses IEEE-488. "Whatever other devices may be available in the future, I would like all instrument makers to equip them with some easy communication links such as USB or Ethernet," he says.
Harpaz's wish is slowly coming to fruition. In 2004, a consortium cofounded by Agilent and VXI Technology Inc. introduced LAN eXtensions for Instrumentation (LXI, www.lxistandard.org). LXI combines features from VXI and GPIB. But it removes some of the more expensive items, such as the card cage, slot 0, and expensive PC-to-instrument communications link (typically $100/m). Ethernet was chosen as the communication link.
Chuck Cimino, the business development manager at Keithley Instruments and an LXI Consortium member, says that USB also was considered, but its deficiencies were disconcerting. With PC architectures changing so quickly, it's unknown how long USB will be supported. Ethernet has a 30-year track record with faster and faster technology that's always backward-compatible.
While LXI instruments can stand alone, the specification defines various module sizes for rack mounting and allows for tying existing VXI and PXI card cages into the system with a network adapter (Fig. 4). Cimino notes that signals enter and exit modules from the front while LAN, power, and trigger connections are located on the rear.
In addition, LXI divides instruments into three classes. Class C (lowest level) provides basic discovery and Web content. (The instrument must be able to serve up a Web page.) Class B includes the IEEE 1588 precision time protocol. And, Class A adds event triggering through an external triggering bus called LXI Trigger.
The LXI Consortium released LXI Revision 1 last September. Agilent, Data Translation, Fluke, Keithley Instruments, Kepco, Lambda, Racal, Teradyne, Yokogawa, and other companies support LXI. Instrument makers like Fluke, says Hammond, are monitoring the activities of the LXI Consortium because LXI could help define Fluke's next-generation products.
LXI is scalable. Engineers can begin with a host computer and one or two instruments and then add devices to run a large test stand. LXI is all about compatibility. Cimino makes an interesting comparison. "Think about what PXI Express will do to your PXI investment. Then think about what 10-Gbit Ethernet will do to your LXI investment. PXI Express instruments won't plug into a PXI mainframe," he says. So, can your old 10-Mbit Ethernet node talk to your 1-Gbit node? Yes, it can!
Unless you're equipping your "workstation" to test the latest silicon chips or the fastest computer buses, you won't need the highest-end instruments available. But you will expect reliability, accuracy, repeatability, and quick responses to signals you're trying to observe. Even more so than today, software and communications in the future will redefine the scope of your instrumentation—your workstation—and communicate your data to wherever it may be needed in the enterprise.
NEED MORE INFORMATION?
Agilent
www.agilent.com
Danaher Motion
www.danahermotion.com
Data Translation
www.datx.com
Fluke Corp.
www.fluke.com
Keithley Instruments
www.keithley.com
Kepco
www.kepco.com
Lambda
www.lambda.com
LeCroy
www.lecroy.com
LXI Consortium
www.lxistandard.org
The MathWorks
www.mathworks.com
National Instruments
www.ni.com
New Star Lasers
www.newstarlasers.com
Racal
www.racalinst.com
Relcom
www.relcominc.com
Schneider Electric
www.schneiderelectric.com
Sphere Research Corp.
www.sphere.bc.ca
Tektronix
www.tektronix.com
Teradyne
www.teradyne.com
Yokogawa
www.yokogawa.com